Carburetor



' s. F. HUNT Aprii 3, 1951 CARBURETOR Original Filed June 17, 1945 OON awuc/nfor,

VOW NOW NOW Ow. v

m: .1 m Om mm. i P y 0mm i, @Q m2 Patented Apr. 3, 1951 UN ITED" STAT ES PATENT F'F-IiCE.

Sc'ottiE. Hhnt,;M:1:-::, i:?:ssignor, by mesne assignments to .Niles-Bement-Pond- Company, West Hartford, Conn a. corporation: ofi" New- Jersey ()riginal application June 17, 1943, Serial No.. 491,096;.now*l?atent' No. 2 4423146, dated May" 2.5;1948,.Dividedrand this application July- 17', 1946 Serial Noe 684,336

The, present application is. a division. ofl my applicationserial No.49l,096,,filed June.1'7;1943',, which matured into Patentv No..2,442,0.46, issued May 25,1948...

This; invention relates to:carburetors for. internalcombustionengines, and particularly to means. for operating such carburetors so as to provide; improved; acceleration. characteristics. of. the .engine.

Ithas previously beenproposed to provide, in, a, carburetor for an. internal combustion engine a device responsive tosthe pressure. in the airin-- duction. system at anpoint downstream; from. the. throttle, and effective. upon. any increase in such.

pressure, such as. accompanies a sudden openingmovement of. the throttles, to. inject. into the; air stream anadditionalsupply of; fuel so. as to. rapidly accelerate:- the. engine;v

It: hasbeen found that with devices of the type, described, the additional supply oi fuel provided. is:not always sufficient. to complete the acceleration;of :the, engineto a speed corresponding to the; new throttle position. Suchia.deviceyprovides;a; momentary additional. supply of. tueh for. the engine; but,- it:. has been; found. that? this additional'supply" of fuel. may be;.Joompletely. dissiipated. before:- the; acceleration: of the. engine? is: completed.

It.:is: therefore: an: object of the present" i-nven-- tion to provide improved means fon suppl'ying additional fuer to i an internal combustion engine during acceleration ofthe engine:

A further" object of theinventionis to'provid'e an improved fuel supply system for an internal combustion engine wherein a first device, is used togive an increasedfuel supply immediately" in response to accelerationof the engine; and .a. second devicefi's used to provi'de'an'other additional fuel supplyafter: a time delay 'f'ollowingsthe initiation of a period of. acceleration.

A further obj 'e'ctt'of the present: invention, is to provide improved means. for supplying additional. fuel toaninterna'lxcombustion engine. upon. ac:- celeration, comprising. a valve. connected. in. parallel with a fueljregulatih'g. valve and controlled as an incident to,acce1eration.of:the .engine;.. A. still' further objticti'stoprovide, insuch. an ar.-' rangement, .a-iuel reservoir having an-outlet con:-- trolled by'an acceleration responsive valve and an acceleration responsive .pump. for: emptying the. reservoir. A. still. further. object. is. to provide such, an. arrangement.-.in. which. the valve; is: main?- tained; open for. a period of. time-.longer-thanthat; required for the pump to empty the reservoir;.

Other objects:- and advantages of thepresent: invention will becomei'apparentlfrom a consideration of the appended specificationgrclaim'sz drawing. in which" The single figurei illustrates; somewhat dia grammatically; an aircraft carburetor embody-- i'ng: the principles ofmy invention. I

Referring" to tliez'drawin'ga there shown a; portion I59 of a carburetor body having extend ing'tl'ierethruan ai'r-passage generally indicatedat-I5I -Ai'r-- enters the passage at an metric, flows thru aventuri res't'riction I53; past athro't' tle I54 and a discharge-nozzle" I55 to an outlet i561 V second airpassage'connects' the: air, inlet' I52: and' thethroatofventuri- I53: This second air, passage maybe tracedfrom the inlet Ii52'thru. a pluralityof impact tubes l'firlj a; ventri'ng I58, a conduit ifi'flianex'pansible chamber: I6],= a restriction I62, angexpensible chamber I63, a conduit I64; a valve chamber, I65; and a conduit. I 66 to' the throatofventuri I 53. 'As. it enters the 'chamber"I'65 from; conduit? I6 3; the air "flow-- ing thru this second passage flowsfp'ast a valve I'GJ COntrolled-by'a bellows IBB'jwYiich'is'mounted in thechamber 165*. The purpose of' the bellows. I'68"is to"compensate*tlie*air flow thru this second". passage" in' accordance with variations; in density The chambers I Wand" I 63are'pa'rtof a metering-unit' III); which includes a casing 'I'II separated bya pair" oftransveise diaphragms I12 and I 1-3i'ntoexpansible -chambers I61, I53 and I14.

motion transmittingt'member I15 is attached to" the centerof'di'aphragm'lngand acts against the center'of'diaphragm I 13? Thecent'e'r of diaphragm I13 is-thereby*movetl to close or open. a. valve portdlli inf'thel'iousin'g I'M. A sprihg'HT biases the member 'I 'lfi tbward'ajposition wherein. the-vaiveport I "lfiis'plbsed by'th'e diaphragm I'I3L.

The fuel supply tcr thercarburetor passes. fromv a pump or other source offuejl under pressure (not shown thru a fuel" regulator unit" I78; a conduit- I'80,'-a mi5 ture" controliunit' 'I'8I,v a jet system-Mia conduit I83; a pressure regulator I84; anda conrluit I 85 to thedischarge nozzle I 55;

Thefuel regulatorunit I78" comprises a l'iousing I '86 separated by a diaphragm IB'I" into" a. pair ofexpansible chamb'ers' IMF and I; Thedi'aphragm I81 carries-at it-sc'ent'er a balanced valve I19 I which control's tlie fiow of fuelfro'm' the'com duit 119 thruthechamber I90. totlieconduit L861 A compression sprin gg I92 biases the valve I 9 I for movementtoward open "position:

The positionof valve I9I is determined by the difference between pressure in the chambers I88 and I90 and by the force exerted by the spring I92. The chambers I88 and I90 are connected by a restriction I 93.

A portion of fuel entering the chamber I90 flows thru the restriction I93, chamber I88, conduit 256, expansible chamber I14 of metering unit I10, and a conduit 200 to an opening 20I in the wall of air passage I5I.

The mixture control unit I8I includes a disc valve 202 fixed on a shaft 203. The shaft 203 may be manually rotated, by means not shown, so that the disc 262 controls the flow of fuel from the conduit I80 to a pair of conduits 204 and 205 leading to the jet system I82 When the shaft 203 is in a position so that fuel can flow only thru the conduit 205 and not thru conduit 204, the mixture control is said to be in the lean position. When the disc valve 252 is in a position such that fuel can flow thru both conduits 20s and 205, the mixture control is said. to be in the rich position.

The conduit 205 conveys fuel to a pair of restructions 206 and 201 in the jet system I82. The restriction 206 is fixed. The restriction 201 is normally closed'by a valve 268 which is biased to closed position by a spring 2I0. The conduit 204 conveys fuel thru a restriction 2II in the jet system' I82. All fuel passing thru the restrictions 201 and 2H must pass thru another restruction 2I2 before emerging from the jet system into the conduit I83.

The pressure regulator unit I84 comprises a casing 2I3 divided by a flexible diaphragm 2I4 into a pair of expansible chambers 2I5 and 2I6. The conduit I83 is connected to the chamber 2I6, and a balanced valve 2I1 attached to the center of the diaphragm 2I4 controls the passage of fuel from the chamber 2 l 6 to the conduit I85. A compression spring 2I8, biases the valve 2I1 toward its closed position. A conduit 220 connects the chamber 2I5 to the conduit I60 and thence to the vent ring I58.

The carburetor is provided with an acceleration control including an acceleration pump 25I, an acceleration responsive valve v252, and a conduit lay-passing the pressure regulator I84. The conduit by-passing the regulator I84 may be traced from circuit I83 thru a conduit/253, a check valve 254, a conduit 255, valve 252, and a conduit 256 to an outlet 259 in the passage I 5|.

The acceleration pum-p 25I includes a housing 251 separated by a diaphragm 258 into a, pair of expansible chambers 260 and 26I. A compression spring 262 biases the diaphragm 258 in a direction to expand the chamber 260 and to collapse the chamber 26I. The chamber 26I is connected thru a conduit 263 to the conduit 255. The chamber 260 isconnected thru conduit 264 to the air passage I5I at a point on the downstream side of throttle I54.

The acceleration responsive valve unit 252 includes a housing 265 separated by a diaphragm 266 into expansible chambers 261 and 268. A compression spring 210 biases the diaphragm 266 in a direction to expand chamber 261 and to collapse chamber 268. A valve 21I is attached to the diaphragm 266 and cooperates with a seat 212 formed in the housing 265.

The chamber 268 is connected thru a conduit 213 to the conduit 264 and thence to the air passage I5I. The chamber 261 is connected thru a restriction 214 to the conduit 264.

4 Operation The operation of the carburetor will first be considered under conditions of constant throttle position, so that the acceleration control is not operating. Under these conditions, the pressure differential established between the inlet I52 and the throat of venturi I53 is communicated to the chambers I6I and I63 of metering unit I 10. This pressure differential acts upwardly on the member I15, and therefore tends to move the diaphragm I13 in a direction to close the port I16. This upward force is opposed by the pressure of the fuel in the chamber I14. As the member I15 moves upwardly, the port I16 becomes more restricted, and the pressure in chamber I14 increases. As the movement of member I15 continues, a point is reached where the downward force due to the pressure in chamber I14 balances that due to the pressure differential between the chambers I6I and I63, and the member I15 remains in that position. It may therefore be seen that a pressure is established in chamber I14 which is a measure of the mass of air flowing thru the passage I5I. This pressure in chamber I14 is communicated back thru conduit 250 to chamber I88 of the fuel regulator I18. I

The pressure in chamber I83 acts on the valve I9I in an opening direction, being aided by the spring I 02 and opposed by the pressure in chamber I90. As the valve I9I is moved by a change in the pressure in chamber I88, the pressure in chamber I90 is varied in a sense to oppose the pressure change in chamber I88. Therefore as the movement of valve I9I continues, a position is reached at which the pressures in chambers I88 and I balance each other and the force of spring I92, and the valve I9I remains in that position. It may therefore be seen that the fuel flow thru the valve I9I is regulated in accordance with the pressure in chamber I88, which is in turn controlled by the mass of air flowing thru the passage I5I.

The mixture control unit I8I is provided to permit the operator of the aircraft in which the carburetor is installed, to select either a rich or lean mixture, depending upon the conditions under which the aircraft is operated. The mixture control unit also may be used by the operator to completely out off the supply of fuel to the carburetor when it is desired to stop the engine.

The jet system I82 provides a fixed restriction in the fuel line. In accordance with well-known hydraulic laws, the flow thru such a fixed restriction is a function of the pressure diiferential across it. The pressure regulator I84, as described in more detail below, operates to maintain a substantially constant outlet pressure on the jet system I82. Therefore the fuel flow thru the jet system, and hence the flow to the carburetor is controlled by the fuel regulator unit I18, which establishes the fuel pressure on the inlet side of the jet system I82 as a function of the air flow thru the passage I5I.

The valve 208 operates to automatically enrich the mixture supplied to the engine under conditions of relatively heavy load. Such heavyv load conditions are accompanied by high rates of air flow thru the passage I5I, which in turn cause a high pressure differential across the jet system I82. When this pressure differential exceeds a value determined by the strength of spring 2I0, the valve 208 opens, thereby increasing the quantity of fuel flowing in proportion to the quantity of air.

aria-see.

51 In the pressure regulatorunit I84 the pres-s sure in chamber 2| 6 is balanced against the'pressure in chamber 24 and the force of spring 2I8. The pressure in chamber 2I5 is relatively low compared to that in chamber 2I6 and to the forcenof sprin 25 8'. Therefore the var a o s of pressure in chamber 2!?) have; relatively little to vent ring I58 is chiefly for the purpose of venting the chamber 2I5 so as to permit ready movement of the valve 2 II.

The pressure downstream from the throttle in the carburetor is communicated to chamber 250 of accelerating pump 25I, while the chamber 26I is subject to the relatively higher fuel pressure on the outlet side of jet system I82. The diaphragm 258 is therefore moved upwardly expanding chamber 2I and filling it with fuel. Since both chambers 25'! and 268 of the valve unit 252 are connected to conduit 264, the pressures on the opposite sides of diaphragm 255 are balanced and the valve 2' is closed by the spring 210.

When the throttle I54 is opened, the pressure downstream from it increases, and this increased pressure is transmitted thru conduit 264 to the chamber 25!] of pump 25I and chamber 258 of valve 252. This increased pressure is also transmitted to chamber 257 of valve 252, but its transmission to that chamber is delayed by the restriction 214. Therefore the pressures in the chambers 25? and 2'68 are unbalanced and the higher pressure in chamber 268 causes the valve 2' to open and remain open for a time determined b the size of restriction 274.

At the same time, the increased pressure in chamber 250 causes that chamber to expand, collapsing the chamber 25I and expelling the fuel therefrom. The check valve 254 then closes, and the fuel expelled from chamber Ztl is thereby forced thru the valve unit 252 to the outlet 259. The size of restriction N4 is preferably chosen so that the valve 2' remains open for a longer time then that required to empty the chamber 26!. As the chamber 2i5l is emptied, the check valve 254 again opens because of the fuel pressure under it, and an additional supply of fuel taken from the downstream side of the jet system I82 is then by-passed thru the valve 2' to the discharge nozzle 259.

Upon a closing movement of the throttle I34, the decreased pressure on the downstream side of it is communicated to chamber 2% thereby collapsing that chamber and expanding the chamber 26! so that the latter is filled with fuel taken from the downstream side of the jet system I82 thru the conduit 253 and check valve 254. This provides a robbing action by which the supply of fuel to the engine is temporarily decreased below the proportion indicated by the quantity of air flowing thru passage I5I. This robbing action enables the engine to decelerate more quickly following the closing movement of the throttle I54.

Since the fuel supply for the acceleration control system is taken from the downstream side of the mixture control valve I8I, the movement of. the valve IBI to its cut-off position will effec- Since the 6i tively stop all fuel flow to the engine. Even though the valve 252' or the pump 25I maybe faulty or leaky, the fuel flow tothe engine may be-completelycut off by the-operation of" valve I8 I While I have shown and described certain pre ferred embodiments of myinvention, other modifications thereof 'will occur to those skilled in the art and I therefore intend that my invention shall be limited only by the appended claims.

' I=*cl'a-im as my invention:

11. In a carburetor for an internal combustion enginehaving an air passage and throttle therefor; and amain conduit for conveying metered fuel= to said passage with valve for controlling the-flow therethru, an acceleration pump comprising an expansible fuel chamber supplied with metered fuel from said main fuel conduit and adapted to discharge said fuel into said air passage, independent of said fuel control valve, in-.

cident to an opening movement of said throttle, a second valve for controlling the discharge of fuel from said fuel chamber, a first expansible air chamber having an intermediate wall adapted to collapse said fuel chamber so as to discharge the fuel therein, and means including a second expansible air chamber having a movable wall adapted to operate said second fuel valve, said expansible air chambers being connected to each other thru a metering restriction and to said air passage posterior to said throttle, whereby, upon a rapid opening of said throttle, said second valve is held open for a longer period of time than is required to collapse said expansible fuel chamber, so that an initial discharge thru said second valve at relatively high pressure is followed by a continuing discharge at a relatively low pressure.

2. In a carburetor for an internal combustion engine, in combination, passage means for the air flowing through said carburetor, a throttle for controllingthe flow of air through said passage means, first and second fuel conduits for conveying fuel to said air passage, first valve means in said first fuel conduit and second valve J means in said second fuel conduit, for respectively controlling the fuel flows therethrough, an expansible fuel chamber connected to said second fuel conduit at a point upstream from said second valve means, a check valve in said second fuel conduit for preventing fuel discharge from said chamber except through said second valve means; a first expansible air chamber having an intermediate wall adapted to collapse said fuel chamber so as to discharge the fuel therein,

' and means including a second expansible air chamber having a movable wall adapted to operate said second valve means, said expansible air chambers being connected to each other through a metering restriction and tosaid air passage posterior to said throttle, whereby said second valve means is held open for a period of time longer than that required to collapse said fuel chamber, so that upon a rapid opening of said throttle, an initial fuel discharge through said r second valve means from said fuel chamber at relatively high pressure is followed by a continuing discharge through said second valve means from said first conduit at relatively low pressure.

3. In a carburetor for an internal combustion engine, in combination, passage means for the air flowing through said carburetor, a throttle for controlling the flow of air through said passage means, a first fuel conduit for conveying fuel to said air passage, first valve means in said conduit for controlling the flow of fluid therethrough, a second fuel conduit connected to bypass said first valve means, second valve means in said second conduit, an expansible fuel champorarily reduce the flow of fuel through said first fuel conduit.

ber connected to said second conduit upstream 5 SCOTT F. HUNT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date Mabee et al May 17, 1932 Cole Dec. 2'7, 1938 Mock et al Mar. 31, 1942 Twyman Dec. 25, 1945 

